Piezo-electrical voltage indicator



Dec. 19, 1922. 1,438,974. E. c. WENTE.

PIEZO-ELECTRICAL VOLTAGE INDICATOR. man Nov. x3, 1920.l

/nvenoh fdwdra 6. Wene 50 tals, such asi Patented Die. 1e, ieaa.

UNET@ STATES l,438,974 PATENT OFFICE.

EDWARD c. WDNTD, or NEW YORK, N. Y.,

ASSIGNOR TO WESTERN ELECTRIC COMPANY,

INCORPORATED, l02E* NEW YORK, N. Y., A CORPORATION OF NEW YORK.

PIEZO-EL'ECTRICAI'..` VOLTAG-E INDICATOR.

Application led November 13, 1920. erial Nc. 423,845.

To all lwhom it may concern:

Be it known that I, EDWARD C. WENTE, a citizen of the United States,residin at New York, in the .county of New ork,

5 State of New York, have invented certain new and useful Improvementsin Piezo- Electrical Voltage Indicators, of which the following is afull, clear, concise, and Aexact description.y

Y This invention relates in general to electric current detectingdevices and particu'- larly to such devicesfor use in connection with'the recording of variations in voltage lntensity.

In apparatus heretofore vavailable for the analysls of complex soundwaves, the analysis of vowel sounds has beenquite lsuccessfully,accomplished. For the analysis of consonant sounds however, it isessential 20 that the apparatus have little or no distortion forfrequencies up to about 10,000 cycles per second. Considerable diicultyhas heretofore been experienced in designing an oscillograph whichv hasa` uniform characteristic. and is free from transient oscillations overthis wide' range of frequencies. s y

The princip-al object of the present -in- Vention is to provide aninstrument simple, accurate,'.positive in wave forms of alternatingcurrents without distortion over a wide range of frequencies. 'A furtherobject of the invention fis to provide a device with which may be used alarger reiector than is ordinarily possible,

so that when the device is used as an oscillograph Vibrator or similarapparatus the intensity of the focusing light will be greatly increased.40v It has been found that in an ordinary oscillograph of the oildamped-type, dueto the change in the viscosity frequenc lcharacteristic1s altered with changes 1n temperature. It is a further object of thisinvention to provide a' device for indicating the intensity of anelectric current which will be unaffected by changes in atmosphericconditions.

It has been quartz are admirably adapted for. constructing vibrators'having great stiffness. :From a considerationof .the f ollowingdetaileddescription ojf-,the invention in its referredv form, taken inlconnection with t e accompanying drawings and-api action, forrecording' vso-tightly as to inter of the oil, the" found thatpiezo-electric' crys 'wilLgve sufficient pended claims, further objectsand features of the invention will be apparent.

Fig. l shows in perspective the invention as applied to an oscillographsystem; and Fig. 2 is a longitudinal cross-sectional View -showing theelectrical connections with the actuating elements.

Referring first to lFig. 1; 3 and 4 are two thin piezo-electric` crystalblades, such as quartz, of the same shape and size, rigidly fastened atone end in a moderately massive block 5; to the other end is attached anoscillograph mirror 6 of proper curvaturel The supporting block 5 mustbe of considerably greater mass than the mirror 6, in order to insure;against vibrations in the block instead of in the mirror. The quartzblades should be cut from the natural crystal in such la way that thegreatest change in length is produced when a potential is ap. pliedbetween the electrodes placed on their lateral faces. The method ofcutting will of course vary with the type of piezo-electric crystalemployed. Quartz, tourmalinev and Rochelle salts, for example, are allpiezo-electrically active, but the method of cutting from the naturalcrystal may dlier in each case. The, electrodes shoul be so connectedinto the circuit that as one blade elongates, the other contracts; willthen be rotated about its center of gravity. ,To prevent buckling, thequartz blades are held between metal slabs 7, which however, are notclam d against the quartz gere with thelr longitudinal movement. i

Inthe sectional view shown 1n Flg. 2. piezo-electrical blades `3 and 4are securely held at one end in the block. The electrodes 9 andI 10 ofmetal foil are placed on the mirror 64 desired, be elec- The air'gapsbetween. the electrodes vand 10 and the metal small so that any ateralvibratlons o blades 3 and 4 are damped by the film of air. This ilm ofair acts as `a cushlon and damping to minimize lateral motion.

.One met sound waves odfor the ,sis of com a .navidadA byynmkim @imlates- 7 are exceedm ly r as applied to the Rankine system forvaryingthe intensity ofthe light falling on a photographic plate inaccordance with a periodic stimulus: Thel light from the source 11 isbrought to focus on the oscillograph mirror 6 by means of the lens 12.After reflection, it is again brought to focus on the photoraphic plateat 13 by means of the lens le.

n the plane surface 15 of the lens 12- 1s placed a grid consisting ofopaque strips which are parallel to each other and yspaced so that thedistances between the adjacent strips are the same and equal to theWidth of the strips. On the plane surface 16 of the lens 14, an exactlysimilar grid is placed. If the miror 6 has the proper curvature and ifthe distances between/the lenses and the mirror are equal, an image ofthe grid at 15 of exactly the same size as the grid itself Will beformed on the plane surface 16. The image of .the grid at 15 may then besuperimposed on the grid at 16. If the mirror 6 is in a position suchthat the image of the strips at 15 falls exactly on clear spaces of thegrid at 16, no light will be transmitted to the point 13, Whereas amaximum amount of light Will be transmitted when the image of the stripsatl15 lies exactly on the strips of the grid at 16. If the equilibriumpoint'A of the angular position at mirror 6 is properly adjusted, thelight transmitted by thev system will be a linear function of theangulary displacement of the mirror about its equilibrium point. Aphotographic record may4 then be, obtained of the motion of the mirror6, by moving the plate past the point 13.

With' a piezo-electric vibrator such as is describedin the presentinvention, a much larger mirror than can ordinarily be used in anoscillograph vibrator may be used, so that the intensity of the lightreaching the film may be greatly increased;V This light may be focuseddirectly on the photographic plate.

By means of this type of vibrator it is possible to record the Wave formof high frequency electric currents Without distortion.

If an oscillograph of this type is used with a condenser-transmitter anda distor-l ;ionless amplifier, la system can be so Vdesigned that thereis practically no distor- ;ion over a Wide range of frequencies. It

vill thus be ,possible to obtain accurate .supporting said blades.

records of consonant sounds. Because ofA the importance of consonantsounds in speech transmission, this method will yield results of agreater value than have heretofore been obtainable.

- While the invention has beenA herein described yin its preferred form,it is noti intended to limit to the specific structure disclosed exceptWithin the pended claims.

That is claimed is:

1.l In a device for indicating the intensity of an electric current, aplurality'of piezo.- electric crystalline blades rigidly supported Scopeof the apat one end. a reflector supported by the free and means ends ofsaid blades, for laterally 2. Ina device for indicatingthe intensity` ofan electric current, a' plurality of piezo'- electric crystalline bladesrigidly supported at one end, a reiector attached to the other movementof said blades to prevent them I from buckling when distorted.

4. In a device for* indicating the intensity of an electric current, asupporting member, a plurality o f piezo-electric crystalline bladessupported at one ber, a member mechanically movable by said blades, andmeans for damping lateral movement of said blades comprising supportingmem-bers on the lateral faces thereof, but separated therefrom by an airgaP- 5. In a device'for'in-dicating the intensity of an electriccurrent, a supporting member,

-a plurality of .piezo-electric crystalline blades supported at one endin sald mem. ber, electrodes disposed on the lateral faces' the end in.saidVV memof said4 blades, supporting members adjacent the lateral facesof said blades, but separated therefrom by air gaps, a reflector mountedon the free end'of said blades, and.

means for connectingsaid electrodes in an electric circuit. I

In witness whereof, I hereunto subscribe my name this 12th day 1920. ilEDWARD C. WENTE..

ios

of November, D.,

